The present invention relates to document-delivery systems, and more particularly to apparatus for inverting documents.
In systems for handling sheets such as sheets of paper it is sometimes desirable to provide the capability of inverting these so that they face in the opposite direction. One example of this is the stacking of a plurality of documents which are serially delivered to a receptacle with an imprinted face upward. These documents will be incorrectly collated with the first-delivered document at the bottom of the stack, unless some means is provided to ensure that the imprinted face will be downwardly oriented (i.e. to flip the document over prior to stacking).
A number of approaches to this problem have been adopted in the prior art. Some of these systems use an array of sheet-engaging mechanisms, such as conveyor belts or rollers which guide the sheets in a circuitous path to achieve the desired shift of orientation. These systems typically occupy an extensive volume and are therefore undesirable in an efficient, compact document-delivery system. Illustrative patents include U.S. Pat. Nos. 4,359,217; 4,264,067; 3,948,385; 4,027,870; and 4,019,435. Another approach utilizes a device to receive the sheet, firmly retain the sheet during rotation or other motion, and release the sheet in an inverted condition. Patents disclosing such systems include, for example, U.S. Pat. Nos. 4,385,756; 4,252,309; and 3,904,192. These devices generally are unduly complex and susceptible to failure, and may provide difficulties in adapting to a variety of sheet lengths.
Still another approach to this problem utilizes a sheet-receiving chute, pocket, or similar structure, together with mechanisms for forcing the sheet into the pocket in one orientation, and receiving or actively withdrawing the sheet in an inverted state. U.S. Pat. No. 3,523,687 to Petersen et al. discloses a series of "angular races", together with a drive roller which frictionally guides the sheet into and out of the races to invert the sheet. The mechanisms disclosed in this reference will tend to encounter difficulties in handling sheets with structural imperfections such as ragged edges, inasmuch as they rely on the engagement between the sheet and a roller having an elastomeric surface. This arrangement may not overcome the paper's tendency to curl in a manner so as to prevent its intended exit.
U.S. Pat. No. 4,078,789 to Kittredge et al. discloses several embodiments wherein a sheet is guided into a chute or chimney, and caused to emerge in an inverted orientation, using a triad of guide rollers at the mouth of the chute. In the embodiment of FIG. 1, the sheet is directed downwardly into a chute, where its presence is detected using a sensor. Upon detection of the sheet, a roller is pivotted into engagement therewith to positively drive the sheet out of the chute. This approach requires apparatus for sensing the sheet, as well as complex mechanisms for engaging the sheet--features which may limit throughput rates and lead to reliability problems. In the embodiment of FIG. 3, which also employs a triad of drive rollers, the sheet is forced upwardly into a chimney, where it strikes a stationary stop member and rebounds, inverted, toward the exit nip. Applicant has observed that systems of this type which largely rely on gravity are inflexible, i.e. difficult to adapt to a variety of sheet lengths and basis weights.
U.S. Pat. No. 4,054,285, to Stange et al., discloses apparatus for guiding the sheet into a rectangular pocket, where it is sensed and forced out of the pocket using a "fluid stream".
Accordingly, it is a primary object of the invention to provide simple, reliable apparatus for inverting documents. Desirably, such apparatus should be well suited to incorporation in a high-speed document-delivery system.
Another object is to avoid the use of elements such as sensor apparatus or complex paper-handling mechanisms. A related object is to achieve a relatively maintainance-free system. An additional related object is avoiding the need to synchronize the operation of the inverting apparatus with the remainder of the system.
Still another object is to allow the adaptation of this system to a variety of parameters in the documents to be handled, including different sheet lengths and basis weights. Such adaptation should not require overly complex adjustments of the document-inverter device.
A further object is the capability of handling substrates having structural imperfections, such as ragged or curled edges.